US3629670A - Electrical contact to silicon carbide - Google Patents

Electrical contact to silicon carbide Download PDF

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Publication number
US3629670A
US3629670A US74545A US3629670DA US3629670A US 3629670 A US3629670 A US 3629670A US 74545 A US74545 A US 74545A US 3629670D A US3629670D A US 3629670DA US 3629670 A US3629670 A US 3629670A
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silicon carbide
yttrium
contact
type region
heating
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US74545A
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Ronald J Perusek
Ralph M Potter
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General Electric Co
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General Electric Co
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L29/00—Semiconductor devices specially adapted for rectifying, amplifying, oscillating or switching and having potential barriers; Capacitors or resistors having potential barriers, e.g. a PN-junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
    • H01L29/02—Semiconductor bodies ; Multistep manufacturing processes therefor
    • H01L29/12—Semiconductor bodies ; Multistep manufacturing processes therefor characterised by the materials of which they are formed
    • H01L29/24—Semiconductor bodies ; Multistep manufacturing processes therefor characterised by the materials of which they are formed including, apart from doping materials or other impurities, only semiconductor materials not provided for in groups H01L29/16, H01L29/18, H01L29/20, H01L29/22
    • H01L29/242—AIBVI or AIBVII compounds, e.g. Cu2O, Cu I
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S438/00—Semiconductor device manufacturing: process
    • Y10S438/931—Silicon carbide semiconductor

Definitions

  • Yttrium metal provides a low-resistance electrical contact to a silicon carbide wafer, useful in the manufacture of solid-state lamps.
  • a preferred method comprises the steps of placing a small piece of yttrium on a silicon carbide wafer, and heating to cause fusion to occur.
  • the invention is in the field of silicon carbide devices having electrical contacts applied to silicon carbide, such as used in solid-state lamps.
  • Solid-state lamps may be made from various materials, including silicon carbide.
  • U.S. Pat. No. 3,458,779 to Drs. Blank and Potter (assigned to the same assignee as the present invention) describes a silicon carbide lamp, in which a wafer of silicon carbide having a PN-junction is attached at its P-side to a metal header to form one electrical connection to the lamp, and the other electrical connection is made by fusing a small .piece of gold-tantalum alloy (dot size) to the N-side of the SUMMARY OF THE INVENTION
  • Objects of the invention are to provide an improved electrical contact to silicon carbide, and to provide such a contact that has low electrical resistance and high mechanical adherence strength.
  • the invention comprises, briefly and in a preferred embodiment, the use of yttrium as an electrical contact material for silicon carbide.
  • yttrium is placed on a wafer of silicon carbide, and the combination is heated until fusion occurs, in an inert atmosphere such as argon or argon containing nitrogen.
  • FIGURE of the drawing is a side view of a preferred arrangement for carrying out the invention.
  • a carbon heater strip 11 is heated by a source 12 of electrical energy.
  • a wafer 13 of silicon carbide shown as having a PN-junetion at the interface of an N- type region 16 and a P-type region 14, is placed, P-side down, on the heater strip 11.
  • a small dot of yttrium metal 17 (generally only a few mils in diameter) is placed on the N-side of the wafer 13 where electrical contact is desired to be made.
  • the heater strip 11 is heated, by electric current from source 12, to cause fusion of the yttrium 17 with the silicon carbide wafer 13.
  • the aforesaid heating and fusion preferably is carried out in an atmosphere of inert gas, such as argon, or argon containing nitrogen.
  • inert gas such as argon, or argon containing nitrogen.
  • the wafer is heated to about 2,lO0 C. until the fusion commences, and then the temperature is reduced to about I,650 C. for a few seconds, and then allowed to cool to room temperature.
  • the process, and the use of yttrium as the contact material achieves an improved electrical contact having a relatively low resistance (about 1 ohm) and increased mechanical adherence to the silicon carbide wafer.
  • the mechanism of achieving the improved contact is believed to be the dissolving of some of the silicon carbide in the yttrium at the peak fusing temperature, followed by regrowth of a thin layer of silicon carbide at the contact interface during the cooling period.
  • Nitrogen present in the ambient atmosphere will tend to dissolve in the molten yttrium and to dope the regrown layer strongly N-type, thus helping to guarantee a low-resistance contact. (However, nitrogen in the ambient is not necessary for a low-resistance contact.)
  • the wafer 13 may be further processed, mounted on a header, and connected to electrical lead wires, as described in the above-mentioned US. Pat. No. 3,458,779.
  • An electrical contact to silicon carbide comprising yttrium metal in contact with the silicon carbide.
  • a method of making an electrical contact to silicon carbide comprising the steps of placing a piece of yttrium metal on said silicon carbide, and heating the combination to cause fusion of the yttrium with the silicon carbide.
  • said silicon carbide is in the form of a wafer having a PN-junction at the interface of a P-type region and an N-type region, said piece of yttrium being placed on the surface of said N-type region.

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  • Engineering & Computer Science (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Power Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Ceramic Engineering (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • General Physics & Mathematics (AREA)
  • Computer Hardware Design (AREA)
  • Resistance Heating (AREA)

Abstract

Yttrium metal provides a low-resistance electrical contact to a silicon carbide wafer, useful in the manufacture of solid-state lamps. A preferred method comprises the steps of placing a small piece of yttrium on a silicon carbide wafer, and heating to cause fusion to occur.

Description

United States Patent Inventors Ronald J. Perusek Chardon;
Ralph M. Potter, Pepper Pike, both oi Ohio 74,545
Sept. 23, 1970 Dec. 21, 1971 General Electric Company Appl. No. Filed Patented Assignee ELECTRICAL CONTACT TO SILICON CARBIDE 8 Claims, 1 Drawing Fig.
US. Cl 317/237, 317/234, 29/576 Int. Cl H0ll l/l4 Field of Search 317/234, 237, 238
Primary Examiner-James D. Kallam AttorneysNorman C. Fulmer, Henry P. Truesdell, Frank L.
Neuhauser, Oscar B. Waddell and Joseph B. Forman ABSTRACT: Yttrium metal provides a low-resistance electrical contact to a silicon carbide wafer, useful in the manufacture of solid-state lamps. A preferred method comprises the steps of placing a small piece of yttrium on a silicon carbide wafer, and heating to cause fusion to occur.
PATENTEUBEBQI zen 3629.670
1TWVTYTOTSI RonaLd J. PeT-usek Ralph M. POt tET" Their- A ti'orneg ELECTRICAL CONTACT TO SILICON CARBIDE BACKGROUND OF THE INVENTION The invention is in the field of silicon carbide devices having electrical contacts applied to silicon carbide, such as used in solid-state lamps.
Solid-state lamps may be made from various materials, including silicon carbide. U.S. Pat. No. 3,458,779, to Drs. Blank and Potter (assigned to the same assignee as the present invention) describes a silicon carbide lamp, in which a wafer of silicon carbide having a PN-junction is attached at its P-side to a metal header to form one electrical connection to the lamp, and the other electrical connection is made by fusing a small .piece of gold-tantalum alloy (dot size) to the N-side of the SUMMARY OF THE INVENTION Objects of the invention are to provide an improved electrical contact to silicon carbide, and to provide such a contact that has low electrical resistance and high mechanical adherence strength.
The invention comprises, briefly and in a preferred embodiment, the use of yttrium as an electrical contact material for silicon carbide. Preferably a small dot of yttrium is placed on a wafer of silicon carbide, and the combination is heated until fusion occurs, in an inert atmosphere such as argon or argon containing nitrogen.
BRIEF DESCRIPTION OF THE DRAWING The single FIGURE of the drawing is a side view of a preferred arrangement for carrying out the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawing, a carbon heater strip 11 is heated by a source 12 of electrical energy. A wafer 13 of silicon carbide, shown as having a PN-junetion at the interface of an N- type region 16 and a P-type region 14, is placed, P-side down, on the heater strip 11. A small dot of yttrium metal 17 (generally only a few mils in diameter) is placed on the N-side of the wafer 13 where electrical contact is desired to be made. The heater strip 11 is heated, by electric current from source 12, to cause fusion of the yttrium 17 with the silicon carbide wafer 13.
The aforesaid heating and fusion preferably is carried out in an atmosphere of inert gas, such as argon, or argon containing nitrogen. The wafer is heated to about 2,lO0 C. until the fusion commences, and then the temperature is reduced to about I,650 C. for a few seconds, and then allowed to cool to room temperature.
The process, and the use of yttrium as the contact material, achieves an improved electrical contact having a relatively low resistance (about 1 ohm) and increased mechanical adherence to the silicon carbide wafer. The mechanism of achieving the improved contact is believed to be the dissolving of some of the silicon carbide in the yttrium at the peak fusing temperature, followed by regrowth of a thin layer of silicon carbide at the contact interface during the cooling period. Nitrogen present in the ambient atmosphere will tend to dissolve in the molten yttrium and to dope the regrown layer strongly N-type, thus helping to guarantee a low-resistance contact. (However, nitrogen in the ambient is not necessary for a low-resistance contact.)
The wafer 13 may be further processed, mounted on a header, and connected to electrical lead wires, as described in the above-mentioned US. Pat. No. 3,458,779.
While a preferred embodiment of the invention, and method for carrying it out, have been described, other embodiments and modifications thereof will become apparent to persons skilled in the art, and will fall within the scope of invention as defined in the following claims.
What we claim as new and desire to secure by Letters Patent of the United States is:
1. An electrical contact to silicon carbide, comprising yttrium metal in contact with the silicon carbide.
2. A contact as claimed in claim 1, in which said yttrium metal is in fusion contact with said silicon carbide.
3. A contact as claimed in claim 1, in which said silicon carbide is in the form of a wafer having a PN-junction at the interface of a Ptype region and an N-type region, said contact being positioned at the surface of said N-type region.
4. A method of making an electrical contact to silicon carbide, comprising the steps of placing a piece of yttrium metal on said silicon carbide, and heating the combination to cause fusion of the yttrium with the silicon carbide.
5. A method as claimed in claim 4, in which said heating comprises bringing the combination to a temperature of about 2,100 C. until fusion commences, reducing the temperature to about 1,650 C. for a few seconds, and allowing to cool.
6. A method as claimed in claim 5, in which said heating is carried out in an atmosphere of argon.
7. A method as claimed in claim 5, in which said heating is carried out in an atmosphere of argon containing nitrogen.
8. A method as claimed in claim 4, in which said silicon carbide is in the form of a wafer having a PN-junction at the interface of a P-type region and an N-type region, said piece of yttrium being placed on the surface of said N-type region.

Claims (7)

  1. 2. A contact as claimed in claim 1, in which said yttrium metal is in fusion contact with said silicon carbide.
  2. 3. A contact as claimed in claim 1, in which said silicon carbide is in the form of a wafer having a PN-junction at the interface of a P-type region and an N-type region, said contact being positioned at the surface of said N-type region.
  3. 4. A method of making an electrical contact to silicon carbide, comprising the steps of placing a piece of yttrium metal on said silicon carbide, and heating the combination to cause fusion of the yttrium with the silicon carbide.
  4. 5. A method as claimed in claim 4, in which said heating comprises bringing the combination to a temperature of about 2, 100* C. until fusion commences, reducing the temperature to about 1,650* C. for a few seconds, and allowing to cool.
  5. 6. A method as claimed in claim 5, in which said heating is carried out in an atmosphere of argon.
  6. 7. A method as claimed in claim 5, in which said heating is carried out in an atmosphere of argon containing nitrogen.
  7. 8. A method as claimed in claim 4, in which said silicon carbide is in the form of a wafer having a PN-junction at the interface of a P-type region and an N-type region, said piece of yttrium being placed on the surface of said N-type region.
US74545A 1970-09-23 1970-09-23 Electrical contact to silicon carbide Expired - Lifetime US3629670A (en)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3715636A (en) * 1972-01-03 1973-02-06 Gen Electric Silicon carbide lamp mounted on a ceramic of poor thermal conductivity
US20110298131A1 (en) * 2010-06-08 2011-12-08 Ethan Hull Yttrium contacts for germanium semiconductor radiation detectors

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1658647A (en) * 1927-04-14 1928-02-07 Gen Electric Alternating-current rectifier
US1708571A (en) * 1925-02-21 1929-04-09 Carborundum Co Rectifying element
US1733519A (en) * 1927-07-23 1929-10-29 Frank N Summers Electric valve
US1994632A (en) * 1933-05-11 1935-03-19 Bell Telephone Labor Inc Asymmetric conductor
US2273704A (en) * 1935-10-10 1942-02-17 Bell Telephone Labor Inc Electrical conducting material

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1708571A (en) * 1925-02-21 1929-04-09 Carborundum Co Rectifying element
US1658647A (en) * 1927-04-14 1928-02-07 Gen Electric Alternating-current rectifier
US1733519A (en) * 1927-07-23 1929-10-29 Frank N Summers Electric valve
US1994632A (en) * 1933-05-11 1935-03-19 Bell Telephone Labor Inc Asymmetric conductor
US2273704A (en) * 1935-10-10 1942-02-17 Bell Telephone Labor Inc Electrical conducting material

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3715636A (en) * 1972-01-03 1973-02-06 Gen Electric Silicon carbide lamp mounted on a ceramic of poor thermal conductivity
US20110298131A1 (en) * 2010-06-08 2011-12-08 Ethan Hull Yttrium contacts for germanium semiconductor radiation detectors
US8729656B2 (en) * 2010-06-08 2014-05-20 Ethan Hull Yttrium contacts for germanium semiconductor radiation detectors

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